Rockwell Automation 1746-FIO4V SLC 500 Fast Analog I/O/ User Manual - Manual (Page 60)

Publication 1746-UM009B-EN-P - September 2007
60 Write Ladder Logic
Brake Monitor Example Program for SLC 5/02 (or later) Processors
Rung 2:2
The next 2 rungs ensure that the analog input value to be scaled remains within the limits of 409 and 2047. This
prevents out-of-range conversion errors in the SCL and PID instructions. The latch bits can be used elsewhere in the
program to identify the particular out-of-range error which occurred.
Rung 2:3
Rung 2:4
Rung 2:6
This rung immediately updates the analog output card driven by the PID’s CV.
Rung 2:7
+END+
Rung 2:5
The PID control variable is the input for the scale instruction. The PID instruction guarantees that the CV remains
within the range of 16383. The CV is scaled to 6242–31208, the numeric range required for a 4–20 mA output signal.
Under
RangeB3
(L)
0
Over
Range
B3
1
GRT
GREATER THAN
Source A
Source B
N7:0
0
2047
LES
LESS THAN
Source A
Source B
N7:0
0
409
MOV
MOVE
Source A
Dest
409
N7:0
0
MOV
MOVE
Source
Dest
2047
N7:0
0
PID
PID
Control Block
Process Variable
Control Variable
Control Block Length
N10:0
N7:0
N10:29
SCL
SCALE
Source
Rate (1/10000)
Offset
Dest
N10:29
0
15239
6242
O:1.0
IOM
IMMEDIATE OUT w MASK
Slot
Mask
Length
O:1.0
FFFF
(L)